(a) Field of the Invention
The present invention relates to cellulose-based fibers and a tire cord including the same.
(b) Description of the Related Art
Nylon, polyester, rayon, and the like are generally used as materials for a tire cord. The rating and use of the tire are limited according to the merits and demerits of the materials.
Nylon fiber is mainly used in tires for heavy-duty trucks that are subjected to heavy loads, or in tires mainly used on irregular surfaces such as unpaved roads, because it has high tensile properties. However, the nylon fiber is unsuitable for a passenger car requiring high speed driving and riding comfort, because it generates intensive heat accumulation inside of the tire, and has a low modulus.
Polyester fiber has good shape stability and a competitive price in comparison with the nylon, its tenacity and adhesive tenacity are being improved by continuous studies, and the amount used in the field of tire cords is tending to increase. However, it is unsuitable for a tire for high speed driving, because there are still limitations in heat resistance, adhesive tenacity, and so on.
Rayon fiber, a regenerated cellulose fiber, shows a superior tensile properties and shape stability at high temperatures. Therefore, the rayon fiber is known as the most suitable material for a tire cord. However, it requires substantial moisture control when preparing the tire, because the strength is severely deteriorated by moisture and the rate of inferior goods is high due to the heterogeneity during preparation of the fiber. First of all, its performance by price (strength by price) is very low in comparison with the other materials, and thus it is only applied to an ultra high speed driving tire or a high-priced tire.
Korea patent publication No. 2002-0085188 discloses a tire cord prepared by using lyocell fibers having superior dry tenacity, wet tenacity, and modulus to rayon fiber. However, there is a disadvantage in that the tensile properties of the lyocell fibers decreases according to repeated fatigue because of higher modulus and lower breaking elongation than the rayon fibers, and the life span of a tire using it decreases.
As disclosed above, the cellulose-based fibers such as rayon and the like have a stiff molecular structure, but there is a problem in that the strength severely deteriorates in processes of twisting and heat-treating because of their low elongation. Therefore, it is needed to develop a tire cord that decreases less in strength even under repeated fatigue while maintaining established tenacity and that can be used for preparing a long lasting tire, and cellulose-based fibers that can be used for the tire cord.